[linux-dvb] Re: Having packet corruptions with DEC2000-t and 2.4

[Holger Waechtler <holger@qanu.de>]

Sergio Moreira wrote:
> I'm having problems with the v2.4 branch of the DVB drivers (pulled
> today from CVS) using a Hauppauge DEC2000-t.
> The device is recognized properly, and I'm able to perform a channel
> scan with dvb-apps/*/scan/.
> On one machine, everything works fine, but on the other I get regular
> checksum errors and missing packets. The machine that doesn't work
> properly is a bit under spec'ed. It has a Crusoe TM5800 clocked at
> 733mhz. From past experience, Crusoes are no good for performance, but
> I wasn't expecting it to be this bad.
I was running this device on a 450MHz x86 notebook successfully, so I 
assume it should work in your setup, too.


> I just do a "tzap -r 'BBC ONE'", and my var/log/messages will get
> constant flooding. I'm not even reading any data from dvr0, just
> running tzap. I modified ttusb_dec.c a little, to print out the first
> 4 bytes of each packet. Looking at the log messages, sometimes some
> packets will start with "00 00" instead of the usual 0x47 Sync byte.
> Whenever there is a checksum error, one packet seems to go missing.
Can you please check in the irq handler whether packets get lost and/or 
marked as errornous?

Are there other devices on the USB bus that eat bandwidth? If so, can 
you please try another USB port or an external USB adapter to be sure 
the problem is not caused by insufficient hardware? Are you using the 
UHCI or the OHCI driver? If you are using UHCI, which one? Some driver 
versions have been known to have problems in their implementation of 
isochronous transfers, maybe you might want to change another version or 
add/enable some debug code in the UHCI/OHCI layer to get an idea where 
the packets get lost.

Holger